Apparatus for cutting a notch in a subsurface formation



June 7, 1966 J. L. HUlTT ET AL 3,254,720

APPARATUS FOR CUTTING A NOTCH IN A SUBSURFACE FORMATION Filed Oct. 8,1964 5 Sheets-Sheet 1 INVENTORS. J/MM/f 1. flu/rr JOSEPH A PE/(AREK June7, 1966 J. L. HUlTT ET AL APPARATUS FOR CUTTING A NOTCH IN A SUBSURFACEFORMATION Filed Oct. 8. 1964 5 Sheets-Sheet 2 INVENTORS. J/MM/E L.HU/TT' JOSEPH L. PE/OLQEK June 7, 1966 .1. HUlTT ETAL APPARATUS FORCUTTING A NOTCH IN A SUBSURFACE FORMATION 5 Sheets-Sheet 5 Filed Oct. 8,1964 INVENTORS J/MM/E L. f/U/TT JOSEPH L. PE/(APEK United States Patent3,254,720 APPARATUS FOR CUTTING A NOTCH IN A SUBSURFACE FORMATION JimmieL. Huitt, Glenshaw, and Joseph L. Pekarek, Penn Hills, Pa., assignors toGulf Research & Development Company, Pittsburgh, Pa., a corporation ofDelaware Filed Oct. 8, 1964, Ser. No. 402,601 6 Claims. (Cl. 16655) Thisapplication is a continuation-in-part of United States Patent No.3,193,012 entitled Method of Cutting a Notch in an Underground FormationPenetrated by a Well, issued July 6, 1965 on application Serial No.113,432, filed May 29, 1961. This application contains material dividedfrom said patent and said application, and the invention describedherein relates to the fracturing of subsurface formations penetrated bya well, and more particularly to apparatus for cutting a notch in suchformations for the initiation of a fracture.

It has become common practice to create fractures extending from theborehole of a well into a subsurface formation to increase theproductive capacity of the well regardless of whether the Well is usedin the primary production of fluids from the subsurface formation or isan injection or production well used in a secondary recovery process.The fractures are created by pumping a liquid down the well and applyinga pressure, usually called the breakdown pressure, adequate to overcomethe tensile strength of the subsurface formation and the weight of theoverburden.

It is important, if the maximum improvement in the capacity of the wellis to be obtained by fracturing, that the fracture be properly locatedand oriented. In the Dismukes Patent No. 2,699,212 a process isdescribed for the accurate location and orientation of the fracture. Inthat process, a notch is cut in the borehole wall to create a plane ofweakness and increase the surface subjected to the pressure applied tothe fracturing fluid to cause the fracture to form as an extension ofthe notch. The notch also lowers the breakdown pressure required tofracture the formation.

It is advantageous to fracture wells that have been cased through thezone to be fractured. The pressure of the fracturing fluid is thenapplied to the formation only at an opening that has been cut in thecasing at the desired location; hence, accurate control of the locationof the point of initiation of the fracture is assured. Notches cut inthe subsurface formation to be fractured are ad- "vantageous infracturing a formation from a well in which casing has been set becauseof the reduced pressure that the breakdown pressure exceeds the pressurethat may be applied to the casing if a notch has not been cut in theborehole wall. It is then necessary to set a packer in the casingisolating the opening through which the fracture is to be made from theremainder of the casing and run tubing through the packer for deliveryof the fracturing fluid into the isolated portion of the casing.

One of the methods that has been widely used for cutting a notch in asubsurface formation for initiation of a fracture employs a fluid whichis directed at a high velocity from a nozzle against the borehole wall.The fluid may be a liquid, which may be a corrosive liquid such as anacid, or a suspension of abrasive particles in a liquid or gas. Thismethod, usually referred to as hydraulic cutting, is faster than thecutting of a notch with a mechanically operated tool. Moreover, thehydraulic cutting of the desired notch does not require a rotary rig, asdo mechanical tools adapted to cut a hori zontal notch, thereby allowinga substantial saving in the cost of the undercutting operation. However,in some instances the marked reduction in breakdown pres- 3,254,720Patented June 7, 1966 sure and accurate location of the fracture that isobtained when -a notch is cut by hydraulic means in an open hole havenot been realized when an abrasive slurry is used to cut the desirednotch in a cased well.

This invention relates to apparatus for hydraulically cutting a notch ina formation penetrated by a cased well for the initiation of a fracturein which an opening of substantial width is cut through the casing, andthere after a hydraulic cutting fluid is discharged from a nozzlethrough the opening in the casing to cut thedesired notch in thesubsurface formation.

ameter of the nozzle opening. In a preferred embodiment of thisinvention, the opening in the casing is cut by a high velocity streamdischarged from one set of nozzles and thereafter second stage nozzleslocated at the midpoint of the opening are made operative and a notch iscut in the formation by a high velocity stream discharged through thesecond set of nozzles.

In the drawings:

FIGURE 1 is a diagrammatic illustration, partially in vertical section,of apparatus in which a mechanical tool is used to cut an opening in thecasing; 1

FIGURE 2 is a vertical sectional view of the cutting tool and nozzleused in the embodiment of the invention illustrated in FIGURE 1;

FIGURE 3 is a vertical sectional view along the section line 33 inFIGURE 2 of the apparatus for cutting the opening in the casing;

FIGURE 4 is a sectional view of an embodiment of this invention in whichthe opening of substantial width in the casing is .cut hydraulically;

FIGURE 5 shows a comparison of the configuration of a notch cut in thesubsurface formation by the apparatus of this invention with notches cutwhen the same nozzles used to cut the notch in the formation are used tocut the opening in the casing;

FIGURE 6 is a longitudinal sectional view taken along the section line6--6 in FIGURE 7 of a preferred em bodiment of this invention shown incondition for cutting the opening in the casing, in which the opening inthe casing and the notch of the formation are out without moving thetool vertically in the hole during the change from one operation to theother;

FIGURE 7 is a sectional view taken along the section line 7-.7 in FIGURE6 showing the orientation of the nozzles for cutting the opening in thecasing;

FIGURE 8 is a horizontal sectional view of the preferred embodiment ofthis invention with the second stage nozzles in operating condition; and

FIGURE 9 is a fragmentary vertical sectional view of the preferredembodiment of this invention taken along section line 9-9 in FIGURE 7.

We have discovered that the removal of a section of the casingsubstantially larger than the diameter of the stream discharged from thenozzle used to cut the notch in the formation prior to cutting the notchin the formation allows the creation of a notch extending a greaterdistance radially from the casing into the formation. The nozzlesordinarily used for the cutting of casing or the cutting of notches insubsurface formations by hydraulic means have a diameter not exceeding Ainch. A preferred nozzle has an opening with a diameter of inch. In theprocess of this invention, the opening cut in the casing has a width atleast four times the diameter of the opening in the nozzle used to cutthe notch in the formation. The maximum width of the opening in thecasing is governed by considerations other than those important to thisinvention. Ordinarily, there is no improvement in the depth or shape ofthe notch cut in the formation if the opening in the casing is more thanabout ten times the diameter of the nozzle used to cut the notch Thewidth of the opening cut in the casing is at least four times the di-.

in the formation. The removal of a section of the casing greater thanapproximately ten times the diameter of the nozzle used to cut the notchin the formation may be objectionable because of the exposure of alarger area OD. casing while a back pressure of 700 p.s.i. wasmaintained inside the %2-inch O.D. casing. The 2-inch pipe was rotatedat a rate of 6 rpm. The cutting action was discontinued periodically andthe depth of the notch of the formation to the fracturing liquid with aresultant 5 Cut in the formation measured. diminishing accuracy oflocation of the fracture. Several diiferent nozzle heads were used tocut the Although the reason for the increased depth of cut Opening inthe casing and the notch in the cement 511T- into the formation madepossible by the process of this rounding the Sue-inch h I11 Testsinvention is not known with certainty, it is believed that and 3 an ofthe nozzles were m the Same heFlzonml when the opening in the casing isthe result only of dis- Plane, e the m nozzles were used for cuttmg thecharging a stream of cutting fluid from the nozzle used Openmg m thecasmg and notch 4 t nozzle head used for cutting the opening III thecasing to cut the notch in the formatlon, the opening in the h d h 1 d ld h l in does not have sufficient area to allow cutting fluid a t tee esarrange m a Splra aroun t e nozz 6 cas g head. In Test No. 5 the nozzlehead had four nozzles to flow back into the borehole of the well afterstriking arranged in a Spiral Similar to the lower nozzle body the outerportlon of the cut without interfering with the illustrated in FIGURENozzle heads with the flow of euttmg field outwardly f nozzle dividualnozzles arranged in the same horizontal plane patently, the baekflow ofhydrauhe fiuld from the Outer were used in every test to cut the notchin the cement. portion of the notch cut into the borehole of the well ish results f the tests are set f th in Table 1 In all not at a highenough velocity to cut the casing and of the tests the nozzles used tocut the notch in the increase the opening in the casing to a width whichwill cement had a diameter of 7 inch.

TABLE I Depth of Notch Beyond Casing After Test Width of N0. of Cuttingfor No. Casing Nozzles for Opening, in. Cutting Notch 7min 12 min 15min. 17 min. 20 min.

eliminate the interference with the outwardly flowing It will be notedfrom tetst No. 1 in which a section /2 stream discharged from thenozzle. inch wide was removed from the casing by means of the A seriesof tests was run to determine the effect of nozzles used to cut thenotch in the target that the maxiincreasing the width of the opening inthe casing through mum diameter of the notch was 14 inches after aZO-minute which a high velocity stream of water and sand is directedcutting period. Because there was no increase in the notch to cut anotch in the subsurface formation. A target diameter after a 20-minutecutting period over the notch was prepared from a 24-inch section of20-inch O.D. diameter after a 15-minute cutting period, the maximumseamless steel casing having a wall thickness of 0.438 notch diameterapparently had been obtained. By ininch. The ends of the casing wereclosed with 20-inch creasing the width of the section removed from the 5/2- extra strong seamless steel welding caps. An opening was inch casingto 1 /8 inch, the diameter of the notch was cut in one of the weldingcaps to receive 5 /2-inch O.D. increased to 17 inches in a 17-minutecutting period. 17 lb./ft. casing which was extended down into thetarget Moreover, the diameter of the notch was increased 2 to a depthabout 4 inches from the bottom of the target inches by increasing thecutting period from 12 to 17 and welded in place at the opening. Thelower end of minutes. Hence, a further increase in the notch diameterthe 5 /2-inch O.D. casing was closed with a 5-inch extra may have beenobtained if a larger cutting period had strong seamless steel weldingcap. Two openings were been used. cut in the end of the target near theopening for the 5 /2- An even greater increase in the diameter of thenotch inch O.D. casing to receive 1 inch couplings. The anwas obtainedwith a cutting tool having four nozzles, as nular space between the 5/2-inch casing and the 20-inch is shown by comparison of Tests Nos. 2and 5. In Run casing was filled with a 15 lb./ gal. neat Portlandcement. No. 5 in which the width of the section removed from The cementwas set under 700 p.s.i. pressure for a period the casing was 1 /2inches, a notch diameter of 19 inches of at least 14 days. An openingoutside of the target was obtained. That notch diameter was equal to theinin the 5 /2-inch casing was fitted with a 2-inch coupling sidediameter of the 20-inch casing used in construction to which suitablevalves were connected for control of the of the target. Moreover, therewas an approximately 3- back pressure during the cutting of the notch inthe casing in h increase in am t r during the last 5 minutes of in thecement surroundin the casing, the cutting period. The area of theformation exposed A 2-inch pipe having a hydraulic nozzle head mounted ythe notch in T st N 5 Was approximately twice the at its lower end todirect an abrasive slurry laterally area of the formation exposed y the1 n notch of against the 5 /z-inch O.D. casing was extended down Test Nn through the 5 /2-inch O.D. casing. Suitable connections Referring toFIGURE 5 in Which the eehfigllratioh of were provided for supplying thehydraulic slurry under the notch 1 cut during Test No. 2 is comparedwith that pressure into the 2-in ch pipe, to allow rotation of the 0fthe notch 2 Cut in Test it ll be ticed that z-i h pipe i hi h 5 -i h 0 Di d to the increased length of the notch is obtained with subtrol theflow from the .5 /2-inch O.D. casing whereby the stalltiany change inWidth- The longer, IlaITOWeI desired pressure could be maintained in theannulus be- Shape of the notch Obtained in Test 5 Provides a t n the 24b pipe d h 5 4 1 0 D i An greater concentration of forces at the apex ofthe notch abrasive slurry of water containing sand in a concentraandmore r ely fiXeS t plane f th fracture. tion of 1 /2 lb./ gal. waspumped down through the 2-inch Moreover, notches formed through narroweropenings pipe and discharged from the nozzle against the 5 /2-inch inthe casing tend to approach the wall of the casing at an acute angle, asa result of which upon application of pressure during the fracturingoperation, substantial forces tending to separate the formation from thecasing are created. The notches formed through wide openings in thecasing approach the outer surface of the casing at an obtuse angle whichminimizes forces tending to separate the casing from the formationduring the subsequent fracturing. The notches formed actually are moreirregular than indicated in FIGURE 5 which indicates an average of theshape of cross sections taken along different radii, and permits a moreaccurate comparison of the two notches.

One embodiment of the invention is illustrated in FIGURES 1 to 4 for themechanical removal of a section of the casing to form the desired wideopening. Referring to FIGURE 1, a well indicated generally by referencenumeral 18 is illustrated with a borehole extending through the pay zone12. Casing 14 is set completely through the pay zone. The well isillustrated with its upper end closed at the surface by a casing head 16on which a blowout preventer 18 is mounted. A T 20 on the upper end ofthe blowout preventer 18 has a lateral outlet for connection to a line22 for discharge of a circulating fluid.

Within the casing near the lower portion of the pay zone 12 is the tool,indicated generally by reference numeral 24, for cutting the opening inthe casing and the notch in the pay zone 12. The tool 24 is connected atits upper end to drill pipe 26 connected to the lower end of a kelly 28which is illustrated extending upwardly from the T 20 through a rotarytable 30 mounted on a rotary rig 32.

Referring to FIGURE 2, tool 24, which is illustrated in verticalsection, is made up of a tubular housing 34 connected at its upper endto a hydraulic nozzle head 36 which is suitably threaded at its upperend for connection to the lower end of the drill pipe 26. Housing 34 hasa central passage 38 extending through it in which a piston 40 isadapted to slide. Piston 40 is urged upwardly by a helical spring 42which engages the lower surface of the piston 40 and a shoulder 44extending from the inner surface of passage 38. Extending downwardlyfrom piston 40 are spaced connecting rods 46 between which an arbor 48extends. A pair of pivot arms 50 adapted to rotate on the arbor 48 areconnected by means of pivot pins 54 to a pair of cutters 56 which arerotatably mounted on an axle 58 extending between opposite faces 'of thehousing 34. One of the pivot arms 50 is connected to the cutter 56 onone side and the other pivot arm 50 to the cutter 56 on the oppositeside of the center line between arbor 48 and axle 58 to cause thecutting elements to move in opposite directions as the piston 40 isforced downwardly. A tubular neck 60 in the piston 40 has an orificeinsert 62 which permits a limited flow through the piston 40.

Hydraulic nozzle head 36 has a central passage 64 extending lengthwisethrough it in which a sleeve 66 is slidably mounted. During the periodwhen a section is cut from the casing, sleeve 66 is held in the upperposition illustrated in FIGURE 2 by a shear'pin 68. A plurality ofnozzle ports 70 adapted to receive nozzle inserts 72 are provided in thewall of the hydraulic nozzle head 36 for the discharge of a cuttingfluid during the cutting of a notch in the formation. Openings 74 in thewall of sleeve 66 are located for alignment with the nozzle port 70 uponshearing of shear pin 68 and movement of the sleeve 66 to its lowerposition.

In the operation of the apparatus illustrated in FIG- URES 1 through 3,the tool 24 is suspended with the cutters 56 at the desired elevation bymeans of drill pipe 26. A circulating liquid is pumped down through thekelly 28 and the drill pipe 26 and through the hydraulic nozzle head 36into the housing 34 while the tool is rotated by means of the kelly 28on rotary table 30. The pressure drop through orifice 62 causes downwardmovement of the piston 40 which in turn causes the cutters 56 to rotateto an extended position at which they engage the casing. The cutters 56are shaped to cut an opening of the desired width in the casing.Rotation of the tool 24 and circulation of the circulating liquid iscontinued until the poston 40 descends to a level below relief ports 76at which position the cutters 56 are fully extended and the desiredopening has been cut completely throughthe casing 14. The pressure onthe circulating liquid drops to indicate when the casing cuttingoperation is completed. Thereafter, the flow of the circulating liquidis stopped and the spring 42 returns the piston 40 to the positionillustrated in FIGURE 2 of the drawings.

The tool is then lowered on the drill pipe 26 a distance adapted tobring the orifice ports 70 in alignment with the opening cut in thecasing by the cutters 56. A ball 78 is dropped down the drill pipe tocome to rest on a valve seat 80 at the bottom of sleeve 66. Liquid isthen pumped into the upper end of the drill pipe under pressuresufficient to shear shear pin 68 and cause sleeve 66 to move downwardlyand bring openings 74 into alignment with the nozzle ports 70. Then,while the tool is rotated by means of the kelly 28 in rotary table 30, ahydraulic cutting fluid such as an abrasive slurry of sand suspended inwater is pumped down the drill pipe 26 and through the nozzle '72 for aperiod adequate to cut the desired notch.

A tool for use in this invention in which both the opening in the casingand the notch are cut hydraulically is illustrated in FIGURE 4.Referring to that figure, the tool, indicated generally by referencenumeral 82, illustrated suspended on the-lower end of a string of tubing84, consists of an upper nozzle head 86 having a plurality of nozzleports 88 positioned in a single horizontal plane. Nozzle inserts 90 of asuitable hard metal such as tungsten carbide are mounted in the ports 88by any suitable means such as the screw threads illustrated in FIGURE 4.Fitting slidably within the upper body 86 is a sleeve 92 having an uppersection of large diameter connected to a lower section of smallerdiameter by a sloping surface 96 which serves as a valveseat. Above thelevel of surface 96 are openings 98 extending through the Wall of sleeve92 in position for alignment with the nozzle ports 88. The sleeve 92 isheld in the upper position illustrated in FIGURE 4 with the openings 98out of alignment with the nozzle ports 88 by a shear pin 100 during theperiod the opening is cut in the casing.

Connected to the lower end of sleeve 92 is a lower nozzle body 102having noozle ports 104 extending through it. The number and location ofthe nozzle ports 104 is designed to cause the stream discharged from thenozzle to overlap and thereby remove a continuous section withoutintervening strips of metal. The number of nozzle ports 104 will bedetermined by the width of opening that is desired in the casing. In theapparatus illustrated in FIGURE 4, the lower nozzle body 102 is providedwith four nozzle ports 104 pointing in directions separated by 90 fromone another. A nozzle insert 106 of suitable hard material is mounted ineach of the nozzle ports 104. The size of the central opening 108 in thelower body 102 is decreased at the lower end of the lower body toprovide a valve seat 110.

In the operation of the apparatus illustrated in FIG-. URE 4, thehydraulic tool 82 is run into the well on tubing 84 to the desireddepth. A ball 112 of proper size to engage the valve seat M0 and closethe lower end of the tool 82 is dropped down the tubing. Thereafter, anabrasive slurry is pumped down the tubing and discharged from thenozzles 104 while the tubing is rotated. Rotation of the lower nozzlebody 102 with the tubing 84 is accomplished by means of a slot 114 inthe lower end of upper nozzle body 86 which is engaged by a key 116extending from the outer surface of the sleeve 92. The rotation of thetool and the pumping of the cutting fluids through the nozzles of thelower nozzle body is continued for a period adequate to cut on openingin the casing. The tool 82 is then lowered a distance adequate to bringthe nozzle ports 88 into alignment with the center of the opening cut inthe casing Wall. A ball 1-18 is then dropped down the tubing to engagesurface 96 to close the lower end of sleeve 92. Liquid pressure isapplied to break the shear pin 100 and move the sleeve 92 to a lowerposition at which passages 98 are in alignment with the nozzle ports 88.Downward movement of the sleeve 92 is limited by a retaining ring 120 atthe lower end of the upper nozzle body. The tool is then rotated asbefore while a cutting fluid is pumped down the tubing and through thenozzles 91 to cut the desired notch in the subsurface formation.

Referring to FIGURE 6 in which the preferred embodiment of thisinvention is illustrated, a cylindrical nozzle head 122 is threaded, asindicated at 124, for connection to the lower end of drill string 26 orother tubing for running into the well. The nozzle head 122 is threadedat its lower end to receive a bushing 12 6 having a central openingthrough which fluids may flow. The diameter of the central openingthrough the bushing is smaller than the inner diameter of the nozzlehead to form a shoulder 127. Slidable within the nozzle head 122 is asleeve 128 having a base plate 130 secured to its lower end. Base plate130 has a central opening 131 extending therethrough and a valve seat133 surrounding the upper end of opening 131. The sleeve 128 is shorterthan the nozzle head 122; hence, the sleeve can slide within the nozzlehead from an upper position illustrated in FIGURE 6 to a lower positionin which the base plate 13%) engages the shoulder 127. During thecutting of an opening in the casing and running of the tool into thewell, the sleeve is held in its upper position by a shear pin 132engaging the nozzle head and the base plate 130. A key 134 extendingfrom the side of the base plate rides in a slot 135 L pirevent rotationof the sleeve relative to the nozzle Nozzle head 122 is drilled andtapped in a spiral arr angement to receive a plurality of first stagenozzles 136 as shown in FIGURE 7. In the apparatus illustrated in thedrawings, four first stage nozzles 136 are oriented at 90 intervals. Asin the case of nozzle inserts 106 illustrated in FIGURE 4, the firststage nozzles 136 are vertically spaced from one another whereby thestreams of abrasive fluid discharged from the nozzles overlap to cut anopening in the casing substantially wider than the diameter of theorifice of the second stage nozzles. In a typical arrangement, thenozzles 136 have inch diameter throats vertically spaced inch from oneanother. The widening pattern of the streams discharged from the nozzlethroats causes the streams to overlap and cut a continuous opening freeof debris from the casing.

Nozzle head 122 is drilled at 138 to receive a plurality of second stagenozzles 140' positioned in a single horizontal plane midway between thecenter lines of the highest and lowest first stage nozzles 136. Thesecond stage nozzles 140 are oriented at 90 intervals from one anotherat an angle of 45 from the first stage nozzles 136. Second stage nozzles140 have a diameter less than A the width of the opening to be cut inthe casing. With the arrangement of first stage nozzles described in thepreceding paragraph, nozzles 140 have a diameter of inch or less.

Ports 142 extending through sleeve 128 are in alignment with the nozzles136 when the sleeve is in the upper position illustrated in FIGURE 6.Openings 144 angularly displaced 45 from the ports 142 extend throughthe sleeve 128 at a position above ports 1 42 to be in alignment withthe nozzles 140 when the sleeve is in the lower position with the baseplate 130 bearing against the bushing 126. A horizontal shoulder 146extends inwardly around the inner surface of the sleeve 128 to provide avalve seat between the ports 142 and openings 144. The

8 opening through the sleeve 128 defined by shoulder 146 is larger thanthe opening 131 through base plate 130.

In the operation of the apparatus illustrated in FIG- URES 6 through 9,the nozzle head 122 is lowered into the Well to the desired depth on thelower end of a string of drill pipe or tubing. A ball 148 of smallerdiameter than the opening defined by shoulder 146 is dropped down thedrill string and engages .the valve seat 133 at the top of the baseplate 130. An abrasive slurry is pumped down the drill string anddischarged through ports 142 and first stage nozzles 136 in a highvelocity stream to cut an opening in the casing. The nozzle head isanchored at the desired depth by a hydraulic hold-down in the drill pipestring immediately above the nozzle head 122. The drill string and toolare rotated during the cutting operation. After a circumferentialopening has been cut in the casing, a ball 150 of a size adapted to seaton shoulder 146 is dropped down the drill string while maintainingpressure on the drill string to keep the holddown operation. The ballprevents flow of liquids through openings 142 and causes the pressure tobuild up within the drill string to a level which breaks shear pin 132.The sleeve 128 moves to the lower position with the openings 14-4 inalignment with second stage nozzles which are centered in thecircumferential opening cut in the casing by the first stage nozzles.The abrasive slurry is discharged through second stage nozzles 14-0against the formation to cut the desired notch in the formation.

It will be noticed that the second stage nozzles 140 are positionednearer the face of the formation than the nozzles 136; thus, the twostage nozzle arrangement illustrated in FIGURES 6 through 9 positionsthe nozzles at the desired stand-off for more efficient cutting as wellas for cutting the wide opening in the casing necessary for cutting aformation notch of substantial depth. The preferred embodiment of theinvention illustrated in FIGURES 6 through 9 has the advantage that novertical movement of the nozzle head is necessary between the firststage cutting of the opening in the casing and the second stage cuttingof the notch in the formation. Because the lower end of the drill stringcan be locked securely in place and maintained in that positionthroughout the operation, the position of the second stage nozzles isfixed and the stream discharging from them can be centered accuratelywithin the opening cut in the casing.

This invention has been described for apparatus adapted to cut acontinuous ring from the casing and a continuous horizontal notch in thesurrounding formation. The invention can also be used for cutting othertypes of holes in the formation for facilitating fracturing. Forexample, it may be desirable to make a series of holes instead of aslot, in the formation hydraulically by not rotating the nozzle duringthe cutting operation. The advantages of this invention can then berealized by cutting a hole in the casing having a substantially largerdiameter than the diameter of the nozzle used to cut the hole in theformation.

We claim:

1. Apparatus adapted to be run into a well on the lower end of pipe forhydraulically cutting an opening in casing of the well and in theformation surrounding the well comprising a tubular nozzle head, asleeve slidable vertically within the nozzle head from an upper positionto a lower position, laterally directed first stage nozzles in thenozzle head vertically spaced from one another a distance to causeoverlapping streams from the nozzles to impinge against the casing, alaterally directed second stage nozzle in the nozzle head positionedsubstantially at the midpoint vertically of the first stage nozzles,said first stage nozzles being constructed and spaced at distances onefrom another such that the streams from said nozzles abrade a strip ofeasing having a width equal to at least four times the diameter of saidsecond stage nozzle, said second stage nozzle being angularly displacedfrom the first stage nozzles, ports in the sleeve positioned foralignment with the first stage nozzles when the sleeve is in the upperposition, an opening in the sleeve angularly displaced from the portsand located above the ports whereby the opening is in alignment with thesecond stage nozzle when the sleeve is in the lower position, releasablemeans for holding the sleeve in the upper position, means for moving thesleeve from the upper to the lower position, and means to preventrotation of the sleeve relative to the nozzle head.

2. Apparatus adapted to be run into a well on the lower end of pipe forhydraulically cutting an opening in casing of a well and the surroundingformation comprising a tubular nozzle head, a plurality of first stagenozzles opening laterally from the nozzle head, said first stage nozzlesbeing vertically displaced from one another a distance adapted todischarge overlapping streams from the nozzles against the casing,laterally opening second stage nozzles in the casing substantially atthe midpoint vertically of the first stage nozzles, said second stagenozzles being displaced angularly from the first stage nozzles andhaving a throat diameter less than one-fourth of the vertical extent ofthe impingement of the overlapping streams against the casing, a sleeveslidable within the casing from an upper position to a lower position,ports in the sleeve positioned for alignment with the sleeve when thesleeve is in its upper position, openings in the sleeve positioned foralignment with the second stage nozzles and positioned above the ports adistance whereby a movement on the sleeve to the lower position theopening is in alignment with the second stage nozzles, releasable meansfor holding the sleeve at its upper position, means for moving thesleeve from the upper position to the lower position, a vertical slot inthe inner wall of the lower portion of the nozzle head, and meansextending from the sleeve into the slot to prevent rotation of thesleeve relative to the nozzle head.

3. Apparatus as set forth in claim 2 in which the second stage nozzlesare positioned radially outward from the first stage nozzles.

4. Apparatus adapted to be run into a well on the lower end of pipe forhydraulically cutting a circumferential opening in the casing of a welland the formation surrounding the well comprising a tubular nozzle headadapted to be run into the well on tubing string, said nozzle headhaving a shoulder extending inwardly near its lower end, a sleeveslidable within the nozzle head from an upper position to a.lowerposition at which the sleeve rests on the shoulder, releasable meansengaging the nozzle head and the sleeve to hold the sleeve in the upperposition, a vertical slot in the inner surface of the nozzle head, a keyextending outwardly from the lower end of the sleeve into the slot toprevent rotation of the sleeve relative to the notch, a plurality oflaterally directed first stage nozzles in the nozzle head verticallydisplaced one from another a distance adapted to direct overlappingstreams outwardly from said nozzles, each of said first stage nozzlesbeing angularly displaced from the others, a plurality of laterallydirected second stage nozzles in the nozzle head, said second stagenozzles being located in a single horizontal plane substantially at themidpoint vertically of the first stage nozzles, said second stagenozzles having a diameter not more than one fourth the ventical sweep ofthe streams directed from the first stage nozzles, ports in the sleevepositioned for alignment with the first stage nozzles when the sleeve isin the upper .position, openings in the sleeve located above the ports a1% distance whereby said openings are in alignment with the second stagenozzles when the sleeve is in the lower position, releasable means forholding the sleeve in the upper position, and means for moving thesleeve from the upper position to the lower position.

5. Apparatus as set forth in claim 4 including a base plate'secured tothe lower end of the sleeve, a passage having a diameter less than theinner diameter of the sleeve extending longitudinally through the baseplate, a valve seat at the upper end of the passage, and a shoulderaround the inner surface of the sleeve between the ports and theopenings therein to form an upper valve seat, said upper valve seathaving a diameter larger than the diameter of the passage in the baseplate.

6. Apparatus adapted to be run into a well on the lower end of pipe forhydraulically cutting an opening in casing of the well and in theformation surrounding the well comprising a tubular nozzle head, asleeve slidable within the nozzle head from an upper position to a lowerposition, a shear pin holding the sleeve in the upper position, stopmeans extending inwardly from the inner surface of the nozzle head tolimit downward movement of the sleeve within the nozzle head, a baseplate secured to the lower end of the sleeve, a vertical passage havinga diameter smaller than the inner diameter of the sleeve extendingthrough the base plate, a valve seat at the upper end of the passage, aplurality of first stage nozzles opening outwardly through the nozzlehead, said first stage nozzles being angularly displaced approximatelyone from another and vertically displaced one from another a distancewhereby the stream discharged from one first stage nozzle overlaps thestream discharged from the vertically adjacent first stage nozzle,second stage nozzles opening outwardly through the nozzle head, saidsecond stage nozzles being located in a single vertical planesubstantially at the midpoint vertically of the first stage nozzles andbeing angularly displaced approximately 90 one from another and 45 fromthe first stage nozzles, said second stage nozzles having a diameter notgreater than one-fourth the vertical sweep of the streams from the firststage nozzles impinging on the casing, ports in the sleeve positionedfor alignment with the first stage nozzles when the sleeve is in theupper position, openings in the sleeve positioned above the ports foralignment with the second stage nozzles when the sleeve is in the lowerposition, a vertical slot in the lower part of the inner wall of thenozzle head, means extending from the base plate into the slot toprevent rotation of the sleeve relative to the nozzle head, and ashoulder extending inwardly from the inner surface of the sleeve betweenthe ports and the openings to form a valve seat having a central openingtherethrough of larger diameter than the vertical passage in the baseplate.

References Cited by the Examiner UNITED STATES PATENTS 2,155,609 4/1925McClendon et a1. 166154 2,236,761 4/1941 Nichols --268 3,066,735 12/1962Zingg 166222 JACOB L. NACKENOFF, Primary Examiner.

BENJAMIN HERSI-I, CHARLES E. OCONNELL,

Examiners.

J. A. LEPPINK, Assistant Examiner.

1. APPARATUS ADAPTED TO BE RUN INTO A WELL ON THE LOWER END OF PIPE FORHYDRAYLICALLY CUTTING AN OPENING IN CASING OF THE WELL AND IN THEFORMATION SURROUNDING THE WELL COMPRISING A TUBULAR NOZZLE HEAD, ASLEEVE SLIDABLE VERTICALLY WITHIN THE NOZZLE HEAD FROM AN UPPER POSITIONTO A LOWER POSITION, LATERALLY DIRECTED FIRST STAGE NOZZLES IN THENOZZLE HEAD VERTICALLY SPACED FROM ONE ANOTHER A DISTANCE TO CAUSEOVERLAPPING STREAMS FROM THE NOZZLES TO IMPINGE AGAINST THE CASING, ALATERALLY DIRECTED SECOND STAGE NOZZLE IN THE NOZZLE HEAD POSITIONEDSUBSTANTIALLY AT THE MIDPOINT VERTICALLY OF THE FIRST STAGE NOZZLES,SAID FIRST STAGE NOZZLES BEING CONSTRUCTED AND SPACED AT DISTANCES ONEFROM ANOTHER SUCH THAT THE STREAMS FROM SAID NOZZLES ABRADE A STRIP OFCASING HAVING A WIDTH EQUAL TO AT LEAST FOUR TIMES THE DIAMETER OF SAIDSECOND STAGE NOZZLE, SAID SECOND STAGE NOZZLES BEING ANGULARLY DISPLACEDFROM THE FIRST STAGE NOZZLES, PORTS IN THE SLEEVE POSITIONED FORALIGNMENT WITH THE FIRST STAGE NOZZLES WHEN THE SLEEVE IS IN THE UPPERPOSITION, AN OPENING IN THE SLEEVE ANGULARLY DISPLACED FROM THE PORTSAND LOCATED ABOVE THE PORTS WHEREBY THE OPENING IS IN ALIGNMENT WITH THESECOND STAGE NOZZLE WHEN THE SLEEVE IS IN THE LOWER POSITION, RELEASABLEMEANS FOR HOLDING THE SLEEVE IN THE UPPER POSITION, MEANS FOR MOVING THESLEEVE FROM THE UPPER TO THE LOWER POSITION, AND MEASN TO PREVENTROTATION OF THE SLEEVE RELATIVE TO THE NOZZLE HEAD.